This invention relates to a capacitor construction having two axially opposed open-mouth cans as housing joined at the open ends in a non-overlapping arrangement via a tapered, insulative, self-locking bushing.
Cylindrical housings for capacitors open at one end that is later closed by covers, bungs, and the like are well-known in the capacitor industry. Likewise well-known are two piece housings where the open ends telescope one over the other. This latter prior art construction has had electrolyte leakage problems. One design requires two-parts of the same length as the capacitance unit so that the open end of one part telescopes against the closed end of the other, providing in effect two housings. This design requires the use of more housing material than is desirable, and it is difficult to seal the overlapped portions to each other. The former prior art design does not suffer from this drawback, although it also is difficult to seal when small units are involved. Because of small can sizes, the internal welding of the terminal tabs and the sealing of the open end requires extra care. Additionally, the closure bung takes up a relatively large proportion of the can space compared with the amount for the capacitor section, such that the resulting volumeric efficiency of the capacitor is low.
A housing that is more volumetrically efficient is composed of a two-piece thermoplastic housing fused together or provided with a tongue-and-groove mating that is then ultrasonically welded. However, these designs require thick walled containers so that some of the volumetric efficiency is lost.
The principle of self-locking tapers is wellknown in the machinery art and is described in various machinery handbooks, e.g. Machinery's Handbook, 17th ed, E. Oberg & F. D. Jones, Industrial Press, N.Y.C. 1964, pg. 1467. For example, twist drills and shank-type milling cutters have self-holding or self-locking taper shanks where the degree of taper is so small that the frictional forces between the shank and the socket is sufficient to drive the tool. The upper limit for a taper to be self-locking or self-holding is generally held to be 16.degree..